• Code: 3900
• Description: Backup memory read/write error (ISC PWB) Read and write data does not match.
• Remedy: Backup memory (ISC PWB) 1. Turn the main power switch off and after 5 seconds, turn it on. 2. Replace the ISC PWB and execute U411.

• Code: 4001
• Description: Polygon motor synchronization error After polygon motor is driven, the ready signal does not turn to L within 30 s. The polygon motor speed won’t stabilize within 10 s.
• Remedy: Polygon motor (LSU) 1. Confirm that the wiring connector is firmly connected and, if necessary, connect the connector all the way in. Polygon motor and Engine PWB (YC15) 2. If the wiring is disconnected, shorted or grounded, replace the wiring. 3. Replace the laser scanner unit.
  Engine PWB 1. Check the engine software and upgrade to the latest, if necessary. 2. Replace the engine PWB.

• Code: 4011
• Description: Polygon motor steady-state error After Polygon motor is stabilized, the ready signal is at the H level for 15 s continuously.
• Remedy: Polygon motor (LSU) 1. Confirm that the wiring connector is firmly connected and, if necessary, connect the connector all the way in. Polygon motor and Engine PWB (YC15) 2. If the wiring is disconnected, shorted or grounded, replace the wiring. 3. Replace the laser scanner unit.
  Engine PWB 1. Check the engine software and upgrade to the latest, if necessary. 2. Replace the engine PWB.

• Code: 4101
• Description: BD initialization error K After Polygon motor is driven, the BD signal is not detected for 1 s.
• Remedy: PD PWB K (LSU) 1. Confirm that the FFC wiring connector is not distorted and connect the FFC wiring all the way in. Laser scanner unit and LSU relay PWB (YC3) LSU relay PWB (YC2) and Engine PWB (YC11) 2. If the FFC wiring is disconnected, replace the FFC wiring. 3. Replace the laser scanner unit.
  Engine PWB 1. Check the engine software and upgrade to the latest, if necessary. 2. Replace the engine PWB.

• Code: 4201
• Description: BD steady-state error K The BD signal is not detected.
• Remedy: PD PWB K (LSU) 1. Confirm that the FFC wiring connector is not distorted and connect the FFC wiring all the way in. Laser scanner unit and LSU relay PWB (YC3) LSU relay PWB (YC2) and Engine PWB (YC11) 2. If the FFC wiring is disconnected, shorted or grounded, replace the FFC wiring. 3. Replace the laser scanner unit.
  Engine PWB 1. Check the engine software and upgrade to the latest, if necessary. 2. Replace the engine PWB.

• Code: 5101
• Description: Main high-voltage error K Measure the inflowing current when Vpp is varied in 3 steps and verify if the difference of the currents of 0 and step 2 is less than 42 (51 if lower highvoltage board).
• Remedy: Drum unit 1. Confirm that the drum or the drum screw can rotate. 2. If it won’t rotate, replace the drum unit. 3. Check that the discharger lamp is properly connected.
  Charger roller unit 1. Check that the high-voltage contacts are not distorted or adhered with foreign objects. 2. Reinstall the chrager roller unit.Or, replace the charger roller unit.
  High voltage PWB 1. Confirm that the wiring connector is firmly connected and, if necessary, connect the connector all the way in. High voltage PWB (YC2) and Engine PWB (YC16) 2. If the wiring is disconnected, shorted or grounded, replace the wiring. 3. Replace the High voltage PWB.
  Engine PWB 1. Check the engine software and upgrade to the latest, if necessary. 2. Replace the engine PWB.

• Code: 6000
• Description: Broken fuser heater wire Fuser thermistor 1 does not reach 100° C/212 °F even after 30 s during warming up. The detected temperature of fuser thermistor 1 does not reach the specified temperature (ready indication temperature) for 420 s in warming up after reached to 100° C/212 °F.
• Remedy: Fuser unit 1. Check that no paper jam is present. 2. Confirm that the wiring connector is firmly connected and, if necessary, connect the connector all the way in. Fuser unit and Engine PWB (YC26) 3. If the wiring is disconnected, shorted or grounded, replace the wiring. 4. Replace the Fuser unit Replace the Fuser unit. (Deteriorated sensitivity due to the toner adhered to the center thermistor.)
  Engine PWB 1. Check the engine software and upgrade to the latest, if necessary. 2. Replace the engine PWB.
  Power source PWB 1. Confirm that the wiring connector is firmly connected and, if necessary, connect the connector all the way in. Power source PWB (YC3) and fuser heater PWB (YC3) Fuser heater PWB (YC2) and feed PWB 1 (YC27) Feed PWB 1 (YC1) and Engine PWB (YC6)
  Fuser heater 1. Replace the fuser unit.

• Code: 6020
• Description: Abnormally high fuser thermistor 1 temperature Fuser thermistor 1 detects a temperature higher than 240°C/464°F for 1 s.
• Remedy: Fuser unit 1. Confirm that the wiring connector is firmly connected and, if necessary, connect the connector all the way in. Fuser unit and Engine PWB (YC26) 2. If the wiring is disconnected, shorted or grounded, replace the wiring. 3. Replace the Fuser unit.
  Engine PWB 1. Check the engine software and upgrade to the latest, if necessary. 2. Replace the engine PWB.